<?php

$a = "k???123456???";
$str = strtr($a, '???', 'ppp');
echo $str, "\n";

$trans = array("h" => "-", "hello" => "hi", "hi" => "hello");
echo strtr("hi all, I said hello", $trans);
//两种行为的模式本质上是不同的:
//1使用三个参数，strtr() 将按字节替换；
//2使用两个参数,即第二给参数是数组这种模式，优先替换更长的子字符串，

 